why does only the last icon display

ive put all 3 of the icons I want to put on my webpage in the html5 file but onlythe last icon coded I displays. I can make it any of the icons I wish(twitter-youtube-facebook)by simple entering in the code last. hers the basic code:

<div id="social-media-icons"><img src ="images/facebook.png"/><img src ="images/youtube.png"/><img src ="images/twitter.png"/><div/> only twitter is displaying but if I put facebook last then it will appear instead.